Battery cell design for preventing internal short circuits from occurring and propagating using positive temperature coefficient (PTC) materials

ABSTRACT

A battery and related methods are described. The battery can include a plurality of battery cell segments. Each of the battery cell segments can include: a positive temperature coefficient (PTC) material whose resistance increases with temperature, an anode segment, a cathode segment, and one or more current limiters. The one or more current limiters of a battery cell segment are configured to conditionally electrically isolate the battery cell segment based on an occurrence of a short circuit within the battery cell segment. The battery can be used to store electrical power and/or provide electrical power to a load.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part to U.S. patent applicationSer. No. 15/464,219, filed Mar. 20, 2017, the contents of which arefully incorporated by reference herein for all purposes.

FIELD

The present disclosure generally relates to electrical batteries, andmore particularly to methods and apparatus related to batteries thathave a plurality of battery cell segments.

BACKGROUND

Batteries are used to store and provide electrical power for aircraft,ground vehicles, personal electronic devices, and otherelectrically-powered devices. A battery can have a positive terminal orelectrode and a negative terminal or electrode. Then, a “load” or devicethat draws power from the battery, can be connected via electricalconductors, such as wires, electrical contacts, and/or cables, to thepositive terminal and the negative terminal in an electrical circuit.The battery can then operate in a discharge mode while providing powerto the load. To charge the battery, a source of electrical power can beelectrically connected to the positive terminal and the negativeterminal in an electrical circuit, and the battery can operate in acharge mode to “charge” or draw and store power from the source. In someapplications, as batteries used in vehicular and electrical powersystems, the battery can be connected to one or more devices that canact as both a load and a source of electrical power to the rest of thecar. While the car is being started, the rest of the car can act as aload to draw power from the car battery. After the car has started, analternator and/or regenerative braking system of the car can act as asource of electrical power to charge the battery.

In some cases, batteries can fail due to environmental conditions,faults in the construction and/or design of the battery, physical damageto the battery, and the (gradual) deterioration of chemicals by thebattery to store and provide current. These faults can lead toelectrical open circuits, where no power is provided to the circuit,and/or battery internal electrical short circuits, where a path of lowelectrical resistance within the battery is created. A short circuit canlead to an unexpectedly large amount of power being provided to acomponent of an electrical circuit, including but not limited to, abattery in the electrical circuit.

SUMMARY

In an example embodiment, a battery is described. The battery includesone or more cells. Each cell includes a plurality of battery cellsegments. Each battery cell segment includes: an anode segment, acathode segment, and one or more current limiters configured toconditionally electrically isolate the battery cell segment based on anoccurrence of a short circuit within the battery cell segment.

In another example embodiment, a method is described. Electrical poweris stored using a battery, where the battery includes one or more cells,where each cell includes a plurality of battery cell segments, and whereeach battery cell segment includes: an anode segment, a cathode segment,and one or more current limiters. A particular battery cell segment isconditionally electrically isolated based on an occurrence of a shortcircuit within the battery cell segment.

In a further example embodiment, a method is described. Electrical poweris provided to a load using a battery, where the battery includes one ormore cells, where each cell includes a plurality of battery cellsegments, and where each battery cell segment includes: an anodesegment, a cathode segment, and one or more current limiters. Aparticular battery cell segment is conditionally electrically isolatedbased on an occurrence of a short circuit within the battery cellsegment.

In yet another example embodiment, a battery is described. The batteryincludes one or more cells. Each cell includes a plurality of batterycell segments. Each battery cell segment includes: a positivetemperature coefficient (PTC) material whose resistance increases withtemperature, an anode segment, a cathode segment, and one or morecurrent limiters configured to conditionally electrically isolate thebattery cell segment based on an occurrence of a short circuit withinthe battery cell segment.

In still another example embodiment, a method is described. Electricalpower is stored using a battery, where the battery includes one or morecells, where each cell includes a plurality of battery cell segments,and where each battery cell segment includes: a positive temperaturecoefficient material whose resistance increases with temperature, ananode segment, a cathode segment, and one or more current limiters. Aparticular battery cell segment is conditionally electrically isolatedbased on an occurrence of a short circuit within the particular batterycell segment.

In even another example embodiment, a method is described. Electricalpower is provided to a load using a battery, where the battery includesone or more cells, where each cell includes a plurality of battery cellsegments, and where each battery cell segment includes: a positivetemperature coefficient material whose resistance increases withtemperature, an anode segment, a cathode segment, and one or morecurrent limiters. A particular battery cell segment is conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment.

It should be understood that the description provided in this summarysection and elsewhere in this document is intended to illustrate aspectsof the present disclosure by way of non-limiting example. Generally, thefeatures, functions, components, and advantages that are discussedherein can be achieved independently in various embodiments or may becombined in yet other embodiments, further details of which aredisclosed in the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of a battery and an electrical load, accordingto an example embodiment.

FIG. 2 is a block diagram of a conventional battery cell.

FIG. 3 is a diagram of the battery cell of FIG. 2 providing current toan electrical load.

FIG. 4 is a diagram of the battery cell of FIG. 2 providing current tothe electrical load based on a uniform ion flow.

FIG. 5 is a diagram of the battery cell of FIG. 2 providing current tothe electrical load based on a degraded ion flow.

FIG. 6 is a diagram of the battery cell of FIG. 2 having an enlargeddegraded area.

FIG. 7 is a diagram of the battery cell of FIG. 2 having a short channelin an enlarged degraded area.

FIG. 8 is a diagram of anode and cathode sheets of the battery cell ofFIG. 2 providing an electron flow to the electrical load while operatingin a normal discharge mode.

FIG. 9 is a diagram of the anode and cathode sheets of the battery cellof FIG. 2 having a short channel.

FIG. 10 is a diagram of a segmented anode sheet and a negative electrodeof a battery cell of the battery of FIG. 1, according to an exampleembodiment.

FIG. 11 is a diagram of a segmented cathode sheet and a positiveelectrode of the battery cell of FIG. 10, according to an exampleembodiment.

FIG. 12 is a diagram of the segmented anode sheet and the negativeelectrode showing an open-circuited current limiter for a failed andisolated segment of the battery cell of FIGS. 10 and 11, according to anexample embodiment.

FIG. 13 is a diagram of the segmented cathode sheet and the positiveelectrode showing an open-circuited current limiter for a failed andisolated segment of the battery cell of FIGS. 10 and 11, according to anexample embodiment.

FIG. 14 is a flowchart of a method for storing electrical power using abattery, according to an example embodiment.

FIG. 15 is a flowchart of a method for providing electrical power usinga battery, according to an example embodiment.

FIG. 16 is a block diagram of a battery and an electrical load,according to an example embodiment.

FIG. 17 is a diagram of a segmented anode sheet and a negative electrodeof a battery cell of the battery of FIG. 16, according to an exampleembodiment.

FIG. 18 is a diagram of a segmented cathode sheet and a positiveelectrode of the battery cell of FIG. 17, according to an exampleembodiment.

FIG. 19 is a flowchart of a method for storing electrical power using abattery, according to an example embodiment.

FIG. 20 is a flowchart of a method for providing electrical power usinga battery, according to an example embodiment.

DETAILED DESCRIPTION

An internal short circuit may occur in a lithium ion battery cell. Suchinternal short circuits are difficult, if not impossible, to sense andmanaged externally and can cause damage to the entire battery. In somecases, internal short circuits can lead to battery fires, and theattendant risk to an environment proximate to the battery. In someexamples, battery chemistry can be changed to reduce electrical activityof the battery and so reduce the risk of an internal short. The drawbackof this approach is that it reduces the battery energy density, makingbatteries relatively larger.

To reduce these risks, a battery with one or more cells, each cellincluding a plurality of battery cell segments is described. Eachbattery cell segment is electrically isolated, and so the use of thesebattery cell segments provides a battery that can prevent and isolate apotential internal short circuit, thus keeping the battery safe andoperational. Each battery cell segment is internal to the battery and/ora cell of the battery, and so no internal sensing is required. Rather,each battery cell segment has one or more current limiters that candetect a short circuit within the battery cell segment and consequentlybreak an electrical circuit. Thus, a battery using battery circuits withcurrent limiters enables automatic detection, location, and isolation of(potential) short circuits within the battery cell segment, keeping theremaining segments of the battery safe and operational.

More particularly, a battery cell segment of a battery can have an anodesegment, a cathode segment, and one or more current limiters configuredto conditionally electrically isolate the battery cell segment based onan occurrence of a short circuit within the battery cell segment. Acurrent limiter of the one or more current limiters can be, or include,one or more electrical components that restrict current flow to amaximum amount. The current limiters can include a current limiterelectrically connected to the anode segment and/or a current limiterelectrically connected to the cathode segment.

A battery cell segment can include one or more insulators thatelectrically isolate the battery cell segment from one or more otherbattery cell segments and/or one or more current collectors. Forexample, an insulator of a battery cell segment can be shaped as aninsulator strip whose thickness is based on the thickness of otherlayers of the battery; e.g., as thick as the total thickness of anode,cathode, separator, and electrolyte layers. A current collector canreceive electrons from either the battery or from a circuit connected tothe battery. For example, a battery cell segment can have an anodecurrent collector electrically connected to the anode segment; and/or acathode current collector electrically connected to the cathode segment.

Current collectors of a battery cell segment can be electricallyconnected to battery electrodes. For example, the anode currentcollector can also be electrically connected to a negative electrode forthe battery, and/or the cathode current collector can also beelectrically connected to a positive electrode for the battery. Thebattery electrodes can electrically connect multiple segments and/orcells of the battery.

A current limiter of a battery cell segment can electrically connect acurrent collector of a segment and a battery electrode; then, thecurrent limiter can restrict an amount of current being provided fromthe battery cell segment (via the current collector) to the electrode orvice versa. In particular, a battery cell segment can have an anodecurrent collector electrically connected to the anode sheet and an anodecurrent limiter electrically connecting the anode current collector to anegative battery electrode and/or a cathode current collectorelectrically connected to the cathode sheet and a cathode currentlimiter electrically connecting the cathode current collector to apositive battery electrode

Examples of segmented batteries include, but are not limited to, lithiumion batteries. Lithium ion batteries can have lithium in one or moreanodes for releasing electrons; i.e., anode sheets and/or anodesegments. The electrons released by the anode(s) can be received atcathode(s); i.e., cathode sheets and/or cathode segments, of theselithium ion batteries. In some cases, an electrolyte can be used asfiller and aid transfer of ions between electrodes of the battery.

Battery cell segments can be used with a wide variety of batterychemistries, including but not limited to lithium-ion based batterychemistries. Examples of other battery chemistries, such as other highenergy density batteries, can use other materials for anodes and/orcathodes than used in lithium ion batteries. Batteries using these otherbattery chemistries can be segmented using the same or similartechniques disclosed herein for segmenting batteries. Batteries ofvirtually any size can utilize battery cell segments, fromrelatively-small batteries, such as used in personal electronics andother applications, to relatively-large batteries used in vehicles,including aircraft, sea craft, and land vehicle and other applications.Thus, the use of segmented batteries can improve battery safety for awide range of batteries and battery applications.

FIG. 1 is a block diagram of battery 100 and electrical load 110,according to an example embodiment. A top portion of FIG. 1 illustratesthat battery 100 and electrical load 110 are connected via wires 102 and104. Battery 100 can store electrical power and provide some or all ofthe stored power to electrical load 110 as electrical power 106 whilebattery 100 is operating in a discharge mode, as indicated by an arrowof electrical power 106 going from battery 100 to electrical load 110.In some examples, electrical load 110 can be replaced by and/or includea power source providing power to battery 100 operating in a chargemode, as indicated by an arrow of electrical power 106 going fromelectrical load 110 to battery 100.

Battery 100 can include c cells, c>0, that include cells 112 a′, 112 a,112 b′, 112 b . . . 112 c′, 112 c which can be connected in seriesand/or parallel. At least one of cells 112 a′, 112 a, 112 b′, 112 b . .. 112 c′, 112 c, can include two or more battery cell segments (BCSs).For example, a upper-central portion of FIG. 1 shows cell 112 c is madeup of n battery cell segments, n>1, which include battery cell segments114 a, 114 b . . . 114 m, 114 n. As such, battery 100 can include aplurality of battery cell segments; e.g., battery cell segments 114 a,114 b, . . . 114 m, 114 n of cell 112 c and battery cell segments incells 112 a′, 112 a, 112 b′, 112 b, . . . (not shown in FIG. 1).

Battery cell segments 114 a, 114 b . . . 114 m, 114 n can be connectedin parallel within cell 112 c. In particular, battery cell segmentsand/or cells of battery 100 can be electrically connected in parallel toelectrodes, such as negative electrode 120 and positive electrode 150.Electrodes 120 and 150 can conduct electrical current, and therebyconduct electrical power, from electrical load 110 to battery 100operating in the charge mode or conduct electrical current/electricalpower to electrical load 110 from battery 100 operating in the dischargemode. Power can be provided to and/or drawn from battery 100 as part ofa circuit that electrically connects negative electrode 120 and positiveelectrode 150; e.g., a circuit including battery 100, wire 102connecting battery 100 with electrical load 110, and wire 104 alsoconnecting battery 100 with electrical load 110.

A lower portion of FIG. 1 shows a top view of neighboring battery cellsegments 114 m and 114 n. Battery cell segments 114 m and 114 n of cell112 c are both electrically connected to negative electrode 120 andpositive electrode 150. Insulator 126 separates battery cell segments114 m and 114 n, which, include respective anode current limiters (CLs)122 m, 122 n, anode current collector (CC) segments 130 m, 130 n, anodesegments 132 m, 132 n, electrolyte fillers 134 m, 134 n, separator sheetsegments (SSSs) 136 m, 136 n, electrolyte fillers 138 m, 138 n, cathodesegments 140 m, 140 n, cathode current collector segments 142 m, 142 n,and cathode current limiters 144 m, 144 n. In some examples, a batterycell segment can have only one current limiter. For example, batterycell segment 114 m can include only anode current limiter 122 m (or onlycathode current limiter 144 m) rather than both current limiters 122 mand 144 m.

Negative electrode 120 is electrically connected to respective batterycell segments 114 m, 114 n via respective anode current limiters 122 m,122 n, which are also electrically connected to respective anode currentcollector segments 130 m, 130 n. Current limiters, such as currentlimiters 122 m, 122 n, 144 m, and 144 n, can include one or moreelectrical components that restrict current flow to a maximum amount.Example current limiters include, but are not limited to, a fuse, apositive temperature-efficient (PTC) current limiter, and a circuitbreaker. A fuse can cause a battery cell segment to be completelyelectrically isolated if current passing through the fuse exceeds thefuse's current limit. A PTC current limiter can have an electricalresistance that increases as temperature of the PTC current limiterincreases. As the electrical resistance of the PTC current limiterincreases with temperature, the PTC current limiter can restrict currentto a designated value, and so protect the battery cell segment. Also,the electrical resistance of the PTC current limiter can decrease as thetemperature of the PTC current limiter decreases, so the PTC currentlimiter can continue functioning as a current limiting device. A circuitbreaker can include an electrical switch, which can be opened toelectrically isolate a battery cell segment if current passing throughthe current passing through the circuit breaker exceeds the circuitbreaker's current limit.

A current limiter can conditionally isolate a battery cell segment whena fault condition, such as an internal short circuit, occurs thatinvolves the battery cell segment. For example, if an internal shortcircuit occurs within battery cell segment 114 m, then arelatively-large amount of current can flow through battery cell segment114 m. In this condition where an internal short circuit occurs, anodecurrent limiter 122 m and/or cathode current limiter 144 m canconditionally electrically isolate battery cell segment 114 m. Otherexamples of conditionally isolating battery cell segments using currentlimiters are possible as well.

Current collector segments 130 m, 130 n, 142 m, 142 n can receiveelectrons from battery 100 and provide the electrons to a circuitconnecting battery 100 to electrical load 110, or vice versa. In someexamples, some or all of current collector segments 130 m, 130 n, 142 m,142 n can be electrically insulated from adjacent current collectors ofother segments.

Anode current collector segments 130 m, 130 n, which are part ofsegmented current collector 130 and of respective battery cell segments114 m, 114 n, are electrically connected to respective anode segments132 m, 132 n. Respective anode segments 132 m, 132 n are separated byrespective electrolytic filler 134 m, 134 n, separator sheet segments136 m, 136 n, and electrolytic filler 138 m, 138 n, from respectivecathode segments 140 m, 140 n. Electrolyte fillers 134 m, 134 n, 138 m,138 n can aid transfer of ions between electrodes of the battery.Respective cathode segments 140 m, 140 n can be electrically connectedto respective cathode current collector segments 142 m, 142 n. Cathodecurrent collector segments 142 m, 142 n are electrically connected torespective cathode current limiters 144 m, 144 n, which alsoelectrically connect respective battery cell segments 114 m, 114 n topositive electrode 150.

An insulator of battery 100 can chemically insulate and/or electricallyinsulate, or resist current flow, between components of battery 100. Asexamples, insulators 124 and 126 electrically insulate battery cellsegment 114 m from adjacent battery cell segments; e.g., insulator 126electrically insulates battery cell segment 114 m from battery cellsegment 114 n. Other components of battery 100 can act as insulators;e.g., container 128 can electrically insulate and otherwise protectbattery cell segment 114 n from an environment outside battery 100.

Separator sheet segments 136 m, 136 n can be made of one or moreseparator materials and provide some protection from a circuit beingformed between an anode segment and a cathode segment of a battery cellsegment while allowing ion flow within battery 100. However, if eitherof separator sheet segments 136 m, 136 n fails to prevent formation of ashort circuit between a respective anode segment 132 m, 132 n andrespective cathode segment 140 m, 140 n, respective anode currentlimiters 122 m, 122 n and/or respective cathode current limiters 144 m,144 n of respective battery cell segments 114 m, 114 n can limit theamount of current provided by a now-short-circuited battery cellsegment.

In some examples, battery 100 can be a lithium ion battery. In theselithium-ion examples, anodes, such as anode segments 132 m, 132 n, canbe made of one or more anode materials such as an intercalated lithiumcompound including, but not limited to, lithium cobalt oxide, lithiumiron phosphate, lithium manganese oxide, and lithium nickel manganesecobalt oxide, lithium phosphate, lithium ferrite, a lithium polymer, andperhaps other materials; e.g., carbonaceous materials includinggraphite, copper foil, tin, misch metal alloys. Other lithium batteriescan use metallic lithium as an anode material. In these lithium-ionexamples, cathodes, such as cathode segments 140 m, 140 n can be made ofone or more cathode materials including, but not limited to, manganesedioxide, carbon monofluoride, iron disulfide, thionyl chloride, brominechloride, sulfur dioxide, sulfuryl chloride, and carbon. Also, in theselithium-ion examples, example materials used as electrolyte fillersinclude, but are not limited to, one or more of lithium perchlorate,propylene carbonate, dimethoxyethane, lithium tetrafluoroborate, gammabutroactone, dioxolane, dimethoxyethane, lithium tetracholoraluminate,thionyl chloride, lithium bromide, sulfur dioxide, and acetonitrile. Inother examples, different anode, electrolyte, and/or cathode materialscan be used in lithium ion batteries.

Insulators of battery 100, such as insulators 124, 126, can be made upof one or more electrically insulating materials, including but notlimited to, polyvinyl chloride, polyethylene terephthalate,polypropylene, tetrafluoroethylene, polyolefin, ceramics, cotton, nylon,polyester, glass, wood, and wood products, such as cardboard or paper.Other insulator sheets and/or materials are possible as well. Separatorsof battery 100, such as separator sheet segments 136 m, 136 n, can bemade of separator materials, where separator materials can be, forexample, one or more materials with a microporous polymer membrane.

In designing battery 100, a minimum number of battery cell segments percell can be determined. Consider that the maximum allowed current of asegment is I_(max) for a duration of time τ, beyond which the segmentmay be subject to an accelerated thermal degradation or damage, wherevalues of I_(max) and τ for a specific battery can be determinedexperimentally according to the specific battery's chemistry. Then, if acell capacity is C, a minimum number n of battery cell segments of acell can be determined using the following equation:

$n = {\frac{c}{I_{\max}\tau}.}$I_(max) and/or τ can also be used in selecting a current limiter foreach segment.

FIG. 2 is a block diagram of conventional battery cell 200. Battery cell200 includes stacked sheets 210, 220, 230, and 240, which can be wrappedinto cylinders to make cylindrical cells or folded into rectangularblocks to make prismatic cells. Battery cell 200 can include insulatoror separator sheet 210 which can be made of one or more electricallyinsulating materials, anode sheet 220 which can be made of one or moreanode materials, separator sheet 230 which can be made of one or moreseparator materials, and cathode sheet 240 which can be made of one ormore cathode materials. Example electrically insulating materials, anodematerials, separator materials, and cathode materials are listed abovein the context of FIG. 1. In battery cell 200, insulator or separatorsheet 210 can protect battery cell 200 from an environment outside thebattery, anode sheet 220 can act as an anode, cathode sheet 240 can actas a cathode, and separator sheet 230 can provide some protection from acircuit being formed between anode sheet 220 and cathode sheet 240 whileallowing ion flow within battery cell 200.

In batteries 100 and 200, insulators and separators differ, asinsulators do not permit lithium ion flow, while separators do permitlithium ion flow. Taking as an example battery 200, if insulator orseparator sheet 210 was not present in battery 200, and if sheets 220,230, and 240 were wrapped from left to right, anode sheet 220 couldtouch cathode sheet 240, and then battery 200 would not operate. Ifinsulator or separator sheet 210 is present as a separator sheet, and ifsheets 210, 220, 230, and 240 were wrapped from left to right to formbattery 200, the cathode and anode layers will have separators on itsinner and outer sides, leading to a workable battery having adouble-sided reaction. If insulator or separator sheet 210 is present asan insulator sheet, and if sheets 210, 220, 230, and 240 were wrappedfrom left to right to form battery 200, then each of anode sheet 220 andcathode sheet 240 has a separator layer on one side and an insulatorlayer on the other side, avoiding double-sided reactions.

FIG. 3 is a diagram of battery cell 200 providing current flow 380 to anelectrical load 110. As battery cell 200 is providing current (ascurrent flow 380) to electrical load 310, battery cell 200 can beconsidered to be in a discharge mode. While in the discharge mode,lithium ions (Li+) shown as black circles in FIG. 3, flow from anodesheet 220 through electrolyte filler 320, separator sheet 230, andelectrolyte filler 330 to cathode sheet 240; that is, from left to rightas shown in FIG. 3.

Battery cell 200 can include two electrodes; a negative electrode 340which can be a source of electron flow 370 from battery cell 200 towardelectrical load 310 while battery cell 200 is in the discharge mode, anda positive electrode 350 which can be a source of current flow 380 frombattery cell 200 toward electrical load 310 while battery cell 200 is inthe discharge mode. Battery cell 200 can also include container 360 toprovide protection from an environment outside the battery.

Battery cell 200 can be in a discharge mode, as mentioned above, or in acharge mode. When battery cell 200 is in the charge mode, lithium ionsof battery cell 200 move in an opposite direction from cathode sheet 240to anode sheet 220 than shown in FIG. 3; that is, the lithium ions fromright to left in FIG. 3. When battery cell 200 is in the charge mode,current flow 380 reverses its flow direction in comparison to whenbattery cell 200 is in the discharge mode.

FIG. 4 is a diagram of battery cell 200 providing current flow 380 toelectrical load 310 based on a uniform lithium ion flow 410. In a normalcondition of battery cell 200 operating in the discharge mode, a uniformlithium ion flow 410 travels from left to right in FIG. 4 from anodesheet 220, across electrolyte filler 320, separator sheet 230, andelectrolyte filler 330 to arrive at cathode sheet 240. In a normalcondition of battery cell 200 operating in the charge mode, uniformlithium ion flow 410 is reversed; that is uniform lithium ion flow 410travels from right to left in FIG. 4.

FIG. 5 is a diagram of battery cell 200 providing current flow 380 toelectrical load 310 based on distorted lithium ion flow 510. Whenbattery cell 200 is operating in a discharge mode, faults can occur thatdistort a uniform lithium ion flow. One such fault is a degradationmechanism involving lithium plating in degraded area 520. If lithiumplating does occur in degraded area 520 of battery cell 200 as shown inFIG. 5, the lithium plating can result in distorted lithium ion flow 510from anode sheet 220 to cathode sheet 240 via separator sheet 230 andelectrolyte fillers 320, 330. Distorted lithium ion flow 510 can causelocal maxima of current density, such as higher current density area 530at the intersection of distorted lithium ion flow 510 and degraded area520.

FIG. 6 is a diagram of battery cell 200 having an enlarged degraded area610. If the lithium plating mentioned in the context of FIG. 4increases, an enlarged degraded area can occur in battery cell 200. Forexample, if battery cell 200 endures prolonged exposure torelatively-high heat, a result in distorted flow of lithium ions acrosselectrodes 340, 350, separator sheet 230, and electrolyte fillers 320,330 can expand. Then, degraded area 520 of FIG. 5 can grow to becomeenlarged degraded area 610 of FIG. 6. As enlarged degraded area 610expands, higher current density area 530 of FIG. 5 can expand to becomeexpanded higher current density area 620 as well.

FIG. 7 is a diagram of battery cell 200 having short channel (SC) 720 inenlarged degraded area 710. If enlarged degraded area 610 continues togrow; i.e., battery cell 200 continues to be exposed to relatively-highheat, to become enlarged degraded area 710, then enlarged degraded area710 can eventually bridge anode sheet 220 and cathode sheet 240,resulting in short channel 720 through enlarged degraded area 710.

Short channel 720 can form a closed current loop with electron flow 730within battery cell 200. Once short channel 720 forms and electron flow730 begins, relatively-few electrons can flow as electron flow 370 toelectrical load 310. Also, some electrons in electron flow 730 withinshort channel 720 can be neutralized by lithium ions 732, 734 attractedfrom electrolyte fillers 320, 330 to enlarged degraded area 710. Theactual number of electrons in electron flow 730 to electrical load 310can depend on the electrical resistance of short channel 720 and theelectrical resistance of electrical load 310. Thus, an internal shortcircuit, such as short channel 720, can be difficult to detect using asensing circuit that is external to (i.e., outside of) battery cell 200.

FIG. 8 is a diagram of anode sheet 220 and cathode sheet 240 of batterycell 200 providing electron flow 370 to electrical load 310 whilebattery cell 200 is operating in a normal discharge mode. In the normaldischarge mode, electrons can be collected at negative electrode 810,which can act as a current collector, from anode sheet 220 of batterycell 200. The electrons can flow as electron flow 730 through electricalload 310 to positive electrode 820, which can act as a currentcollector. Electrons arriving at positive electrode 820 can be uniformlydistributed across cathode sheet 240. In the discharge mode, lithium ionflow (not shown in FIG. 8) can start at anode sheet 220, continue acrossa separator sheet, such as separator sheet 230, and arrive at cathodesheet 240.

FIG. 9 is diagram of anode sheet 220 and cathode sheet 240 of batterycell 200, when battery cell 200 has short channel 910. In a dischargemode with an internal short circuit such as short channel 910, electronscan be collected at negative electrode 810 from anode sheet 220 ofbattery cell 200, just as when battery cell 200 is in a normal dischargemode. However, when battery cell 200 has an internal short circuit,electrons can flow via short channel 910 to cathode sheet 240 instead offlowing to electrical load 310, leading to inhibited electron flow 920through electrical load 310. The electrons arriving at cathode sheet 240can be collected at positive electrode 820 and distributed throughoutcathode sheet 240, as indicated by the arrows from short channel 910 tocathode sheet 240 and through positive electrode 820. Typically,electrical resistance through short channel 910 is much less than anelectrical resistance through electrical load 310, and so most, if notall, electrons flow through short channel 910 rather than flow throughelectrical load 310, leading to inhibited electron flow 920.

FIG. 10 is a diagram of segmented anode sheet 1010 and negativeelectrode 1040 of battery cell 112 c of battery 100, according to anexample embodiment. As indicated in FIGS. 1 and 10-13, battery cell 112c is a segmented battery cell having n battery cell segments, n>1. InFIG. 10, the segments of anode sheet 1010 are shown as anode segments1020 a, 1020 b, 1020 c, 1020 d, 1020 e, 1020 f, 1020 g, 1020 h . . .1020 n. The anode segments are electrically insulated from each other byinsulators 1024 a, 1024 b, 1024 c, 1024 d, 1024 e, 1024 f, 1024 g, 1024h . . . 1024 n. For example, anode segment 1020 b is electricallyinsulated from anode segment 1020 a by insulator 1024 a and iselectrically insulated from anode segment 1020 c by insulator 1024 b.

Anode segments 1020 a, 1020 b, 1020 c, 1020 d, 1020 e, 1020 f, 1020 g,1020 h . . . 1020 n are connected to anode current collector 1030, whichis segmented so that each segment of anode current collector 1030 isconnected to a corresponding segment of anode sheet 1010. Further, eachsegment of anode current collector 1030 is both electrically isolatedfrom other anode current collector segments and connected to negativeelectrode 1040 via an anode current limiter (ACL). For example, FIG. 10shows that: anode segment 1020 a of anode sheet 1010 is connected toanode current collector segment 1032 a of anode current collector 1030,anode current collector segment 1032 a is also connected to anodecurrent limiter 1022 a, and anode current limiter 1022 a is alsoconnected to negative electrode 1040. FIG. 10 also shows that eachsegment of anode current collector 1030 is electrically insulated fromother anode current collector segments by insulators 1024 a, 1024 b,1024 c, 1024 d, 1024 e, 1024 f, 1024 g, 1024 h . . . 1024 n; e.g., anodecurrent collector segment 1032 a is separated by insulator 1024 a fromadjacent anode current collector segment 1032 b.

When battery 100 is in a normal discharge mode, electrons are collectedat segmented anode current collector 1030 from anode segments 1020 a,1020 b, 1020 c, 1020 d, 1020 e, 1020 f, 1020 g, 1020 h . . . 1020 n ofanode sheet 1010. The collected electrons flow from segmented anodecurrent collector 1030 through anode current limiters 1022 a, 1022 b,1022 c, 1022 d, 1022 e, 1022 f, 1022 g, 1022 h, . . . 1022 n to negativeelectrode 1040. These electron flows are illustrated in FIG. 10 byarrows from anode sheet 1010 to anode current collector 1030, arrowsfrom anode current collector 1030 through anode current limiters 1022 a. . . 1022 n to negative electrode 1040. The electrons then flow fromnegative electrode 1040 to electrical load 110 and then as electron flow1050 to a cathode sheet, which is shown in FIG. 11.

FIG. 11 is a diagram of segmented cathode sheet 1110 and positiveelectrode 1140 of battery cell 112 c, according to an exampleembodiment. As indicated in FIGS. 1 and 10-13, battery cell 112 c has nbattery cell segments, n>1. In FIG. 11, the segments of cathode sheet1110 are shown as cathode segments 1120 a, 1120 b, 1120 c, 1120 d, 1120e, 1120 f, 1120 g, 1120 h . . . 1120 n. The cathode segments areelectrically insulated from each other by insulators 1124 a, 1124 b,1124 c, 1124 d, 1124 e, 1124 f, 1124 g, 1124 h . . . 1124 n. Forexample, cathode segment 1120 b is electrically insulated from cathodesegment 1120 a by insulator 1124 a and is electrically insulated fromcathode segment 1120 c by insulator 1124 b. In some examples, insulators1024 a, 1024 b, 1024 c, 1024 d, 1024 e, 1024 f, 1024 g, 1024 h, . . .1024 n can be part of the same insulator as respective insulators 1124a, 1124 b, 1124 c, 1124 d, 1124 e, 1124 f, 1124 g, 1124 h, . . . 1124 n;i.e., an insulator sheet (or other configuration of an insulator) canhave one end separating anode segments of anode sheet 1010 and anotherend separating cathode segments of cathode sheet 1110, while theinsulator sheet can also separate electrolyte filler layers andseparators as well, thus ensuring that no electrons, ions, and/or massflow across the insulator.

Cathode segments 1120 a, 1120 b, 1120 c, 1120 d, 1120 e, 1120 f, 1120 g,1120 h . . . 1120 n are connected to cathode current collector 1130,which is segmented so that each segment of cathode current collector1130 is connected to a corresponding segment of cathode sheet 1110.Further, each segment of cathode current collector 1130 is connected topositive electrode 1140 via a cathode current limiter (CCL). Forexample, FIG. 11 shows that: cathode segment 1120 a of cathode sheet1110 is connected to cathode current collector segment 1132 a of cathodecurrent collector 1130, cathode current collector segment 1132 a is alsoconnected to cathode current limiter 1122 a, and cathode current limiter1122 a is also connected to positive electrode 1140. FIG. 11 also showsthat each segment of cathode current collector 1130 is electricallyinsulated from other cathode current collector segments by insulators1124 a, 1124 b, 1124 c, 1124 d, 1124 e, 1124 f, 1124 g, 1124 h, . . .1124 n; e.g. cathode current collector segment 1132 a is separated byinsulator 1124 a from adjacent cathode current collector segment 1132 b.

When battery 100 is in a normal discharge mode, electrons flow fromanode sheet 1010 as electron flow 1150 to positive electrode 1140.Electrons at positive electrode 1140 then flow through cathode currentlimiters 1122 a, 1122 b, 1122 c, 1122 d, 1122 e, 1122 f, 1122 g, 1122 h,. . . 1122 n to the segmented cathode current collector 1130, and thenfrom the current collector segments to cathode segments 1120 a, 1120 b,1120 c, 1120 d, 1120 e, 1120 f, 1120 g, 1120 h, . . . 1120 n of cathodesheet 1110. These electron flows are illustrated in FIG. 11 by arrowsfrom electron flow 1150 from electrical load 110 to positive electrode1140, through to cathode current limiters 1122 a . . . 1122 n,continuing to cathode current collector 1130, and then to cathodesegments 1120 a . . . 1120 n of cathode sheet 1110.

A battery cell segment of battery 100, such as a segment of battery cell112 c, can include an anode segment of anode sheet 1010 and cathodesegment of cathode sheet 1110. For example, one battery cell segment ofbattery 100 can include: (a) anode segment 1020 a, anode currentcollector segment 1032 a, and anode current limiter 1022 a that isconnected to negative electrode 1040, and (b) cathode segment 1120 a,cathode current collector segment 1132 a, and cathode current limiter1122 a that is connected to positive electrode 1140. Other examplebattery cell segments of battery 100 can include corresponding pairs ofanode and cathode segments (e.g., anode segment 1020 b paired withcathode segment 1120 b), pairs of anode and cathode current collectorsegments (e.g., the anode current collector segment attached to anodesegment 1020 b paired with the cathode current collector segmentattached to cathode segment 1120 b, and pairs of anode and cathodecurrent limiters (e.g., anode current limiter 1022 b paired with cathodecurrent limiter 1122 b), as shown in FIGS. 10 and 11.

Note that battery 100 can include separators and electrolyte fillers asshown regarding battery cell segments 114 m, 114 n of FIG. 1, eventhough FIGS. 10-13 do not show separators and electrolyte fillersregarding battery cell 112 c. Additionally, non-electrode components ofbattery cell 112 c including, but not limited to, anode sheet 1010 andcathode sheet 1110, current collectors 1030 and 1130, current limiters1022 a, 1022 b, . . . 1022 n and 1122 a, 1122 b . . . 1122 n, and anyseparators and electrolyte fillers, can be appropriately packaged andsealed into a container such as container 128; e.g., for use as abattery cell unit. Then electrodes of battery 100, such as negativeelectrode 1040 and positive electrode 1140, can be at least partiallyoutside of the container to enable electrical connections with batterycell 112 c.

FIG. 12 is a diagram of segmented anode sheet 1010 and negativeelectrode 1040 showing an open anode current limiter 1222 for failed andisolated battery cell segment 1220 of battery cell 112 c, according toan example embodiment. Open anode current limiter 1222 can include anopen circuit that disables current from flowing through open anodecurrent limiter 1222. FIG. 12 shows an example of anode sheet 1010 ofbattery cell 112 c while operating in the discharge mode when aninternal short circuit, shown as short channel 1210, occurs in batterycell segment 1220 that includes anode segment 1020 h. If short channel1210 occurs within battery cell segment 1220 while battery 100 isdischarging, most, if not all, electrons flowing from anode segment 1020h will flow through anode current limiter 1022 h, exceeding a maximumamount of current allowed through anode current limiter 1022 h.Exceeding the maximum amount of current allowed can cause anode currentlimiter 1022 h to open (i.e., have an open circuit) and become openanode current limiter 1222. Once anode current limiter 1022 h opens tobecome open anode current limiter 1222, the open anode current limiter1222 electrically isolates battery cell segment 1220. In the meantime,the other battery cell segments that include anode segments 1020 a, 1020b, 1020 c, 1020 d, 1020 e, 1020 f, 1020 g, and 1020 n continue tooperate normally.

Thus, the presence of short channel 1210 causes battery cell segment1220 to fail. Further, the opening of open anode current limiter 1222 asa consequence of short channel 1210 causes battery cell segment 1220 tobe electrically isolated. As such, open anode current limiter 1222 canconditionally electrically isolate battery cell segment 1220 based on anoccurrence of a short circuit within battery cell segment 1220, such theoccurrence of short channel 1210 in battery cell segment 1220.

FIG. 13 is a diagram of segmented cathode sheet 1110 and positiveelectrode 1140 showing an open cathode current limiter 1322 for failedand isolated battery cell segment 1220 of battery cell 112 c, accordingto an example embodiment. Open cathode current limiter 1322 can includean open circuit that disables current from flowing through open cathodecurrent limiter 1322. FIG. 13 shows an example of cathode sheet 1110 ofbattery cell 112 c while operating in the discharge mode when aninternal short circuit, shown as short channel 1210, occurs in batterycell segment 1220 that includes cathode segment 1120 h. If short channel1210 occurs within battery cell segment 1220 while battery 100 isdischarging, most, if not all, electrons flowing to cathode segment 1120h will flow through cathode current limiter 1122 h, exceeding a maximumamount of current allowed through cathode current limiter 1122 h.Exceeding the maximum amount of current allowed can cause cathodecurrent limiter 1122 h to open and become open cathode current limiter1322. Once cathode current limiter 1122 h opens to become open cathodecurrent limiter 1322, the open cathode current limiter 1322 electricallyisolates battery cell segment 1220. In the meantime, the other batterycell segments that include cathode segments 1120 a, 1120 b, 1120 c, 1120d, 1120 e, 1120 f, 1120 g, and 1120 n can continue to operate normally.

Thus, the presence of short channel 1210 causes battery cell segment1220 to fail. Further, the opening of open anode current limiter 1322 asa consequence of short channel 1210 causes battery cell segment 1220 tobe electrically isolated. As such, open cathode current limiter 1322 canconditionally electrically isolate battery cell segment 1220 based on anoccurrence of a short circuit within battery cell segment 1220, such theoccurrence of short channel 1210 in battery cell segment 1220.

Further, battery 100 can recover from a short channel being formed inone (or in other cases, multiple) faulty battery cell segment(s) byopening current limiters of the faulty battery cell segment(s), such asopen anode current limiter 1222 and/or open cathode current limiter 1322of battery cell segment 1220, while any non-faulty battery cell segmentscan continue to operate normally. As such, battery 100 likely canprovide at least a limited amount of power even if a fault occurs, suchas a short channel or other short circuit. Additionally, as faultybattery cell segment 1220 is electrically isolated from other batterycell segments, the likelihood that short channel 1210 will expand toother battery cell segments of battery 100 is reduced.

FIG. 14 is a flowchart of method 1400 for storing electrical power usinga battery, according to an example embodiment. Method 1400 can becarried out using a segmented battery such as battery 100. Method 1400can begin at block 1410, where a battery can store electrical power. Thebattery can include one or more cells. Each cell can include a pluralityof battery cell segments, where each battery cell segment can include:an anode segment, a cathode segment, and one or more current limiters,such as discussed above in the context of at least FIGS. 1 and 10-13.

In some embodiments, a current limiter of the one or more currentlimiters can include a fuse, such as discussed above in the context ofat least FIG. 1. In other embodiments, the one or more current limiterscan include at least one of: a current limiter electrically connected tothe anode segment and a current limiter electrically connected to thecathode segment, such as discussed above in the context of at leastFIGS. 1 and 10-13.

In still other embodiments, each battery cell segment can furtherinclude one or more current collectors, such as discussed above in thecontext of at least FIGS. 1 and 10-13. In some of these embodiments, theone or more current collectors can include at least one of: an anodecurrent collector electrically connected to the anode segment and acathode current collector electrically connected to the cathode segment,such as discussed above in the context of at least FIGS. 1 and 10-13. Instill other of these embodiments, a particular current collector of theone or more current collectors can be electrically connected to anelectrode, such as discussed above in the context of at least FIGS. 1and 10-13. In particular, the particular current collector can beelectrically connected to the electrode using a particular currentlimiter of the one or more current limiters, such as discussed above inthe context of at least FIGS. 1 and 10-13. In further embodiments, eachbattery cell segment can further include a current collector of the oneor more current collectors electrically connected to a current limiterof the one or more current limiters, such as discussed above in thecontext of at least FIGS. 1 and 10-13. In particular, each battery cellsegment can further include an anode current collector electricallyconnected to the anode sheet; and an anode current limiter electricallyconnected to the anode current collector, such as discussed above in thecontext of at least FIGS. 1, 10, and 12. In still further embodiments,each battery cell segment can further include a cathode currentcollector electrically connected to the cathode sheet and a cathodecurrent limiter electrically connected to the cathode current collector,such as discussed above in the context of at least FIGS. 1, 11, and 13.

At block 1420, a particular battery cell segment can be conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment, such as discussed above in thecontext of at least FIGS. 1, 12, and 13.

In some embodiments, conditionally electrically isolating the particularbattery cell segment can include conditionally electrically isolatingthe particular battery cell segment using a current limiter electricallyconnected to the anode segment of the particular battery cell segment,such as discussed above in the context of at least FIGS. 1 and 12.

In other embodiments, conditionally electrically isolating theparticular battery cell segment can include conditionally electricallyisolating the particular battery cell segment using a current limiterelectrically connected to the cathode segment of the particular batterycell segment, such as discussed above in the context of at least FIGS. 1and 13.

In further embodiments, method 1400 can further electrically isolatingthe particular battery cell segment from one or more other battery cellsegments of the plurality of battery cell segments using one or moreinsulator sheets, such as discussed above in the context of at leastFIGS. 1, 12, and 13.

In yet other embodiments, method 1400 can further include: electricallyconnecting at least two battery cell segments of the plurality ofbattery cell segments using one or more electrodes, such as discussedabove in the context of at least FIGS. 1 and 10-13. In particular, aparticular battery cell segment of the at least two battery cellsegments can include at least one of: an anode current collectorelectrically connected to the anode segment and to a negative electrodeof the one or more electrodes; and a cathode current collectorelectrically connected to the cathode segment and to a positiveelectrode of the one or more electrodes, such as discussed above in thecontext of at least FIGS. 1 and 10-13. In further examples, the anodecurrent collector can be electrically connected to the negativeelectrode via an anode current limiter of the one or more currentlimiters; and the cathode current collector can be electricallyconnected to the positive electrode via a cathode current limiter of theone or more current limiters, such as discussed above in the context ofat least FIGS. 1 and 10-13.

FIG. 15 is a flowchart of method 1500 for providing electrical powerusing a battery, according to an example embodiment. Method 1500 can becarried out using a segmented battery such as battery 100. Method 1500can begin at block 1510, where a battery can provide electrical power toa load. The battery can include one or more cells. Each cell can includea plurality of battery cell segments, where each battery cell segmentcan include: an anode segment, a cathode segment, and one or morecurrent limiters, such as discussed above in the context of at leastFIGS. 1 and 10-13.

In some embodiments, a current limiter of the one or more currentlimiters can include a fuse, such as discussed above in the context ofat least FIG. 1. In other embodiments, the one or more current limiterscan include at least one of: a current limiter electrically connected tothe anode segment and a current limiter electrically connected to thecathode segment, such as discussed above in the context of at leastFIGS. 1 and 10-13.

In still other embodiments, each battery cell segment can furtherinclude one or more current collectors, such as discussed above in thecontext of at least FIGS. 1 and 10-13. In some of these embodiments, theone or more current collectors can include at least one of: an anodecurrent collector electrically connected to the anode segment and acathode current collector electrically connected to the cathode segment,such as discussed above in the context of at least FIGS. 1 and 10-13.

In further examples, a particular current collector of the one or morecurrent collectors can be electrically connected to an electrode, suchas discussed above in the context of at least FIGS. 1 and 10-13. Inadditional examples, the particular current collector can beelectrically connected to the electrode using a particular currentlimiter of the one or more current limiters, such as discussed above inthe context of at least FIGS. 1 and 10-13.

In further examples, each battery cell segment can further include acurrent collector of the one or more current collectors electricallyconnected to a current limiter of the one or more current limiters, suchas discussed above in the context of at least FIGS. 1 and 10-13. Inparticular, each battery cell segment can further include an anodecurrent collector electrically connected to the anode sheet; and ananode current limiter electrically connected to the anode currentcollector, such as discussed above in the context of at least FIGS. 1,10, and 12. Each battery cell segment can further include a cathodecurrent collector electrically connected to the cathode sheet and acathode current limiter electrically connected to the cathode currentcollector, such as discussed above in the context of at least FIGS. 1,11, and 13.

At block 1520, a particular battery cell segment can be conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment, such as discussed above in thecontext of at least FIGS. 1, 12, and 13.

In some embodiments, conditionally electrically isolating the particularbattery cell segment can include conditionally electrically isolatingthe particular battery cell segment using one of: a current limiterelectrically connected to the anode segment of the particular batterycell segment, and a current limiter electrically connected to thecathode segment of the particular battery cell segment, such asdiscussed above in the context of at least FIGS. 1, 12, and 13.

Segmented Batteries with PTC Materials

FIG. 16 is a block diagram of a battery 1600 and an electrical load 110,according to an example embodiment. Segmented batteries, such as battery1600, can utilize positive temperature coefficient (PTC) materials intheir construction. A positive temperature coefficient material is amaterial that has one or more properties; e.g., electrical resistance,which increase when the material's temperature is increased. Example PTCmaterials whose electrical resistances increase when the PTC material'stemperature increases include, but are not limited to, a thermoplasticpolymer (i.e., “PTC rubber”), barium titanate, barium carbonate, andtitanium oxide.

In the construction of a segmented battery, a PTC material of battery1600 can replace and/or be included with insulator materials, such asinsulators 124 and 126 of battery 100. In some cases, the PTC materialof battery 1600 can also include one or more active materials toincrease battery cell energy density. An active material can includepositively charged material or negatively charged material, wherepositively charged material is termed cathode active material herein,and where negatively charged material is termed cathode active materialherein. Example cathode active materials include, but are not limitedto, lithium cobalt oxide (LiCoO₂), lithium cobalt phosphate (LiCoPO₄),lithium iron oxide (LiFeO₂), lithium iron phosphate (LiFePO₄), lithiumiron silicate (Li₂FeSiO₄), lithium manganese dioxide (LiMnO₂), lithiummanganese nickel oxide (Li₂Mn₃NiO₈), and lithium manganese nickel oxide(Li₂Mn₃NiO₈). Example cathode active materials include, but are notlimited to, graphite and lithium titanate (Li₄Ti₅O₁₂). For example, in acathode segment of a segmented battery, a sheet, layer, and/or otherarrangement of PTC material can be used with a mix of PTC material andone or more cathode active materials. As another example, in an anodesegment of a segmented battery, a sheet, layer, and/or other arrangementof PTC material can be used with a mix of PTC material and one or moreanode active materials.

To determine a mix of PTC material with one or more cathode activematerials for a battery cell a mass ratio of PTC materials can bedetermined where the mass ratio of PTC materials is sufficiently highsuch that an average resistivity ρ_(av) of PTC and cathode materials ata critical temperature T_(c) is no larger than a critical resistivityρ_(c). The critical temperature T_(c) can be a temperature value belowwhich the battery cell operates normally and above which the batterycell may experience an accelerated degradation and/or an internal shortcircuit; i.e., a short channel may be formed in the battery cell.

The critical temperature T_(c) can be experimentally determined. OnceT_(c) is determined, a critical resistivity ρ_(c_cathode) of a mix ofPTC and cathode active materials; e.g., for use in a cathode segment ofa segmented battery cell, can be determined using Inequality (1) below:

$\begin{matrix}{{\rho_{av}\left( T_{c} \right)} = {\frac{{{\rho_{ptc}\left( T_{c} \right)} \cdot M_{ptc}} + {{\rho_{cathode}\left( T_{c} \right)} \cdot M_{cathode}}}{M_{ptc} + M_{cathode}} \leq \rho_{c\_ cathode}}} & (1)\end{matrix}$where:

-   -   ρ_(ptc)(T_(c)) is: a resistivity of the PTC material in the mix        at the critical temperature T_(c),    -   M_(ptc) is a mass ratio of the PTC material in the mix,    -   ρ_(cathode)(T_(c)) is a resistivity of the cathode material in        the mix at the critical temperature T_(c), and    -   M_(cathode) is a mass ratio of the cathode material in the mix.

Also, a critical resistivity ρ_(c_anode) of a mix of PTC and anodeactive materials; e.g., for use in an anode segment of a segmentedbattery cell, can be determined using Inequality (2) below:

$\begin{matrix}{{\rho_{av}\left( T_{c} \right)} = {\frac{{{\rho_{ptc}\left( T_{c} \right)} \cdot M_{ptc}} + {{\rho_{anode}\left( T_{c} \right)} \cdot M_{anode}}}{M_{ptc} + M_{anode}} \leq \rho_{c\_ anode}}} & (2)\end{matrix}$where:

-   -   ρ_(ptc)(T_(c)) is a resistivity of the PTC material in the mix        at the critical temperature T_(c),    -   M_(ptc) is a mass ratio of the PTC material in the mix,    -   ρ_(anode)(T_(c)) is a resistivity of the anode material in the        mix at the critical temperature T_(c) and    -   M_(anode) is a mass ratio of the anode material in the mix.

The use of PTC materials whose electrical resistance increases withtemperature to separate battery segments can provide increasedelectrical resistance between battery segments as temperatures increase.As a battery segment typically increases in temperature when the batterysegment faults, the use of PTC materials to separate battery segmentsenhances battery segment protection during faults. Addition of activematerials to PTC materials can allow for partial replacement of activematerials removed by PTC layers, thereby increasing battery cell energydensity. In some cases, use of PTC materials mixed with active materialscan maintain (or even increase) battery cell energy density whileproviding enhanced electrical resistance between segments during batteryfaults.

Battery 1600 of FIG. 16 is closely related to battery 100 discussedabove and depicted in at least FIG. 1. Unless explicitly statedotherwise below, battery 1600 performs the same functionality asdescribed for battery 100; e.g., both batteries 100 and 1600 can operatein a charge mode to draw electrical power from a source and can operatein a discharge mode to provide electrical power to an electrical load.And, unless explicitly stated otherwise below, each component sharing acommon reference number for battery 100 and battery 1600 performs thesame functionality as described above in the context of battery 100;e.g., negative electrode 120 performs the same functionality for bothbatteries 100 and 1600.

Like battery 100, battery 1600 can include c cells, c>0, such as cells112 a′, 112 a, 112 b′, 112 b . . . 112 c′, 112 c which can be connectedin series and/or parallel. Also like battery 100, at least one of cells112 a′, 112 a, 112 b′, 112 b . . . 112 c′, 112 c of battery 1600 caninclude two or more battery cell segments. For example, an upper-centralportion of FIG. 16 shows that cell 112 c of battery 1600 is made up of nbattery cell segments, n>1, which include battery cell segments 114 a,114 b . . . 114 m, 114 n. As such, battery 1600 can include a pluralityof battery cell segments; e.g., battery cell segments 114 a, 114 b, . .. 114 m, 114 n of cell 112 c and battery cell segments in cells 112 a′,112 a, 112 b′, 112 b, . . . (not shown in FIG. 16).

A lower portion of FIG. 16 shows a top view of neighboring battery cellsegments 114 m and 114 n of battery 1600. Battery cell segments 114 mand 114 n of battery 1600 are similar to battery cell segments 114 m and114 n described above in the context of battery 100. However, batterycell segments 114 m and 114 n of battery 1600 are separated by one ormore layers of PTC material 1626, while corresponding battery cellsegments 114 m and 114 n of battery 100 are separated by insulator 126.

PTC material 1626 can include PTC materials, anode active materials,and/or cathode active materials. For example, a portion of PTC material1626 shown above separator sheet segments (SSSs) 136 m, 136 n in FIG. 16can be part of and/or separate one or more anode segments. Then, theportion of PTC material 1626 shown above separator sheet segments 136 m,136 n may include PTC material and perhaps anode active material.Similarly, a portion of PTC material 1626 shown below separator sheetsegments 136 m, 136 n can be part of and/or separate one or more cathodesegments, and so the portion of PTC material 1626 shown below separatorsheet segments 136 m, 136 n can include PTC material and perhaps cathodeactive material.

FIG. 17 is a diagram of a segmented anode sheet 1710 and a negativeelectrode 1040 of a battery cell 112 c of battery 1600, according to anexample embodiment. As also indicated in FIG. 16, battery cell 112 c ofbattery 1600 has n battery cell segments, n>1. Segmented anode sheet1710 is closely related to segmented anode sheet 1010 discussed aboveand depicted in at least FIG. 10. Unless explicitly stated otherwisebelow, each component sharing a common reference number for segmentedanode sheet 1010 and segmented anode sheet 1710 performs the samefunctionality as described above in the context of segmented anode sheet1010; e.g., negative electrode 1040 performs the same functionality forsegmented anode sheet 1710 as performed for segmented anode sheet 1010

While segmented anode sheet 1710 is similar to and performs similarfunctionality to segmented anode sheet 1010, segmented anode sheet 1710does differ from segmented anode sheet 1010. For example, anode segmentsof segmented anode sheet 1710 are electrically insulated from each otherby PTC and anode active materials, while anode segments of segmentedanode sheet 1010 are electrically insulated from each other byinsulators. In particular, anode segments of segmented anode sheet 1710are electrically insulated from each other by PTC materials with anodeactive materials 1724 a, 1724 b, 1724 c, 1724 d, 1724 e, 1724 f, 1724 g,1724 h . . . 1724 n. For example, anode segment 1020 b of segmentedanode sheet 1710 is electrically insulated from anode segment 1020 a ofsegmented anode sheet 1710 by PTC material with anode active material1724 a and is electrically insulated from anode segment 1020 c ofsegmented anode sheet 1710 by PTC material with anode active material1724 b. In some embodiments, some or all of PTC materials with anodeactive materials 1724 a, 1724 b, 1724 c, 1724 d, 1724 e, 1724 f, 1724 g,1724 h . . . 1724 n do not include anode active materials; that is, someor all of 1724 a, 1724 b, 1724 c, 1724 d, 1724 e, 1724 f, 1724 g, 1724 h. . . 1724 n only have PTC material.

FIG. 18 is a diagram of a segmented cathode sheet 1810 and a positiveelectrode 1140 of battery cell 112 c of battery 1600, according to anexample embodiment. As also indicated in FIGS. 16 and 17, battery cell112 c of battery 1600 has n battery cell segments, n>1. Segmentedcathode sheet 1810 is closely related to segmented cathode sheet 1110discussed above and depicted in at least FIG. 11. Unless explicitlystated otherwise below, each component sharing a common reference numberfor segmented cathode sheet 1110 and segmented cathode sheet 1810performs the same functionality as described above in the context ofsegmented cathode sheet 1110; e.g., positive electrode 1140 performs thesame functionality for segmented cathode sheet 1810 as performed forsegmented cathode sheet 1110.

In particular, current limiters of battery 1600 perform the samefunctionality for segmented anode sheet 1710 and segmented cathode sheet1810 as discussed above for respective segmented anode sheet 1010 andsegmented cathode sheet 1110 of battery 100. Further, if a short channeloccurs within a particular battery cell segment of battery 1600 whilebattery 1600 is discharging, an anode current limiter and/or a cathodecurrent limiter of the particular battery cell segment of battery 1600can be caused to open, thereby conditionally electrically isolating theparticular battery cell segment in the same fashion discussed above inat least in the context of battery 100 and FIGS. 12 and 13. Further,battery cell segments of battery 1600 other than the particular batterycell segment can continue to operate normally in the same fashiondiscussed above in at least in the context of battery 100 and FIGS. 12and 13.

While segmented cathode sheet 1810 is similar to and performs similarfunctionality to segmented cathode sheet 1110, segmented cathode sheet1810 does differ from segmented cathode sheet 1110. For example, cathodesegments of segmented cathode sheet 1810 are electrically insulated fromeach other by PTC and cathode active materials, while cathode segmentsof segmented cathode sheet 1110 are electrically insulated from eachother by insulators. In particular, cathode segments of segmentedcathode sheet 1810 are electrically insulated from each other by PTCmaterials with cathode active materials 1824 a, 1824 b, 1824 c, 1824 d,1824 e, 1824 f, 1824 g, 1824 h . . . 1824 n. For example, cathodesegment 1120 b of segmented cathode sheet 1810 is electrically insulatedfrom cathode segment 1120 a of segmented cathode sheet 1810 by PTCmaterial with cathode active material 1824 a and is electricallyinsulated from cathode segment 1120 c of segmented cathode sheet 1810 byPTC material with cathode active material 1824 b. In some embodiments,some or all of PTC materials with cathode active materials 1824 a, 1824b, 1824 c, 1824 d, 1824 e, 1824 f, 1824 g, 1824 h . . . 1824 n do notinclude cathode active materials; that is, some or all of 1824 a, 1824b, 1824 c, 1824 d, 1824 e, 1824 f, 1824 g, 1824 h . . . 1824 n only havePTC material.

In some examples, PTC materials with cathode active materials 1824 a,1824 b, 1824 c, 1824 d, 1824 e, 1824 f, 1824 g, 1824 h . . . 1824 n ofsegmented cathode sheet 1810 can be part of the PTC material asrespective PTC material with anode active material 1724 a, 1724 b, 1724c, 1724 d, 1724 e, 1724 f, 1724 g, 1724 h . . . 1724 n of segmentedanode sheet 1710; i.e., a sheet, layer, and/or other configuration ofPTC material can have one end separating anode segments of segmentedanode sheet 1710 and another end separating cathode segments ofsegmented cathode sheet 1810. The PTC material sheet can also separateelectrolyte filler layers and separators as well, thus ensuring that noelectrons, ions, and/or mass flow across the PTC material. In some ofthese examples, the end of the PTC material sheet separating anodesegments of segmented anode sheet 1710 includes anode active materialsand/or the end of the PTC material sheet separating cathode segments ofsegmented cathode sheet 1810 includes cathode active materials.

Note that battery 1600 can include separators and electrolyte fillers asshown regarding battery cell segments 114 m, 114 n of FIG. 16, eventhough FIGS. 17 and 18 do not show separators and electrolyte fillersregarding battery cell 112 c of battery 1600. Additionally,non-electrode components of battery cell 112 c of battery 1600including, but not limited to, anode sheet 1710 and cathode sheet 1810,current collectors 1030 and 1130, current limiters 1022 a, 1022 b, . . .1022 n and 1122 a, 1122 b . . . 1122 n, and any separators andelectrolyte fillers, can be appropriately packaged and sealed into acontainer such as container 128; e.g., for use as a battery cell unit.Then electrodes of battery 1600, such as negative electrode 1040 andpositive electrode 1140, can be at least partially outside of thecontainer to enable electrical connections with battery cell 112 c ofbattery 1600.

FIG. 19 is a flowchart of method 1900 for storing electrical power usinga battery, according to an example embodiment. The battery of method1900 can be a segmented battery having PTC material; e.g., battery 1600.Method 1900 can begin at block 1910, where the battery can storeelectrical power. The battery includes one or more cells, each cellincluding a plurality of battery cell segments, where each battery cellsegment includes a PTC material whose resistance increases withtemperature, an anode segment, a cathode segment, and one or morecurrent limiters, such as discussed above in the context of at leastFIGS. 16-18. For example, the PTC material can be arranged in one ormore sheets or layers within the battery.

In some embodiments, a current limiter of the one or more currentlimiters includes a fuse, such as discussed above in the context of atleast FIGS. 1 and 16. In other embodiments, the one or more currentlimiters can include at least one of: a current limiter electricallyconnected to the anode segment and a current limiter electricallyconnected to the cathode segment, such as discussed above in the contextof at least FIGS. 1, 10-13, and 16-18.

In still other embodiments, the PTC material is one or more of:thermoplastic polymer, barium titanate, barium carbonate, and titaniumoxide, such as discussed above in the context of at least FIG. 16. Ineven other embodiments, the PTC material includes an active material. Insome of these embodiments, the active material includes a cathode activematerial associated with the cathode segment, such as discussed above inthe context of at least FIG. 16. In other of these embodiments, thecathode active material includes one or more of: a material includinglithium cobalt oxide, a material including lithium cobalt phosphate, amaterial including lithium iron oxide, a material including lithium ironphosphate, a material including lithium iron silicate, a materialincluding lithium manganese dioxide, a material including lithiummanganese nickel oxide, and a material including lithium manganesenickel oxide, such as discussed above in the context of at least FIG.16. In even other of these embodiments, the active material includes ananode active material associated with the anode segment, such asdiscussed above in the context of at least FIG. 16. In further of theseembodiments, the anode active material includes one or more of: amaterial including graphite and a material including lithium titanate,such as discussed above in the context of at least FIG. 16.

In yet other embodiments, each battery cell segment further includes oneor more current collectors, and where the one or more current collectorsinclude at least one of: an anode current collector electricallyconnected to the anode segment; and a cathode current collectorelectrically connected to the cathode segment, such as discussed abovein the context of at least FIGS. 1, 10-13, and 16-18. In some of theseembodiments, each battery cell segment further includes: a currentcollector of the one or more current collectors electrically connectedto a current limiter of the one or more current limiters, such asdiscussed above in the context of at least FIGS. 1, 10-13, and 16-18.

In still even other embodiments, at least two battery cell segments ofthe plurality of battery cell segments are electrically connected usingone or more electrodes, such as discussed above in the context of atleast FIGS. 1, 10-13, and 16-18. In some of these embodiments, aparticular battery cell segment of the at least two battery cellsegments includes at least one of: an anode current collectorelectrically connected to the anode segment and to a negative electrodeof the one or more electrodes; and a cathode current collectorelectrically connected to the cathode segment and to a positiveelectrode of the one or more electrodes, such as discussed above in thecontext of at least FIGS. 1, 10-13, and 16-18. In other of theseembodiments, the anode current collector is electrically connected tothe negative electrode via an anode current limiter of the one or morecurrent limiters; and the cathode current collector is electricallyconnected to the positive electrode via a cathode current limiter of theone or more current limiters, such as discussed above in the context ofat least FIGS. 1, 10-13, and 16-18.

In yet even other of these embodiments, the anode segment is separatedfrom the cathode segment by a separator immersed in an electrolytefiller, where the one or more current limiters are connected to thecathode segment and/or the anode segment, and where the PTC layer ispositioned to separate a battery cell segment from other battery cellsegments of the plurality of battery cell segments, such as discussedabove in the context of at least FIGS. 16-18. For example, the separatorcan be made of one or more herein-described separator materials.

At block 1920, a particular battery cell segment can be conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18. In some embodiments, conditionallyelectrically isolating the particular battery cell segment can includeconditionally electrically isolating the particular battery cell segmentusing a current limiter electrically connected to the anode segment ofthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18. In other embodiments, conditionallyelectrically isolating the particular battery cell segment can includeconditionally electrically isolating the particular battery cell segmentusing a current limiter electrically connected to the anode segment ofthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18.

In some embodiments, method 1900 can also include: electricallyisolating the particular battery cell segment from one or more otherbattery cell segments of the plurality of battery cell segments usingthe PTC material, such as discussed above in the context of at leastFIG. 18.

FIG. 20 is a flowchart of a method 2000 for providing electrical powerusing a battery, according to an example embodiment. The battery ofmethod 1900 can be a segmented battery having PTC material; e.g.,battery 1600. Method 2000 can begin at block 2010, where the battery canprovide electrical power to a load. The battery includes one or morecells, each cell including a plurality of battery cell segments, whereeach battery cell segment including” a PTC material whose resistanceincreases with temperature, an anode segment, a cathode segment, and oneor more current limiters, such as discussed above in the context of atleast FIGS. 16-18. For example, the PTC material can be arranged in oneor more sheets or layers within the battery.

At block 2010, a particular battery cell segment can be conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18. In some embodiments, a current limiter ofthe one or more current limiters includes a fuse, such as discussedabove in the context of at least FIGS. 1 and 16. In other embodiments,the one or more current limiters can include at least one of: a currentlimiter electrically connected to the anode segment and a currentlimiter electrically connected to the cathode segment, such as discussedabove in the context of at least FIGS. 1, 10-13, and 16-18.

In still other embodiments, the PTC material is one or more of:thermoplastic polymer, barium titanate, barium carbonate, and titaniumoxide, such as discussed above in the context of at least FIG. 16. Ineven other embodiments, the PTC material includes an active material. Insome of these embodiments, the active material includes a cathode activematerial associated with the cathode segment, such as discussed above inthe context of at least FIG. 16. In other of these embodiments, thecathode active material includes one or more of: a material includinglithium cobalt oxide, a material including lithium cobalt phosphate, amaterial including lithium iron oxide, a material including lithium ironphosphate, a material including lithium iron silicate, a materialincluding lithium manganese dioxide, a material including lithiummanganese nickel oxide, and a material including lithium manganesenickel oxide, such as discussed above in the context of at least FIG.16. In even other of these embodiments, the active material includes ananode active material associated with the anode segment, such asdiscussed above in the context of at least FIG. 16. In further of theseembodiments, the anode active material includes one or more of: amaterial including graphite and a material including lithium titanate,such as discussed above in the context of at least FIG. 16.

In yet other embodiments, each battery cell segment further includes oneor more current collectors, and where the one or more current collectorsinclude at least one of: an anode current collector electricallyconnected to the anode segment; and a cathode current collectorelectrically connected to the cathode segment, such as discussed abovein the context of at least FIGS. 1, 10-13, and 16-18. In some of theseembodiments, each battery cell segment further includes: a currentcollector of the one or more current collectors electrically connectedto a current limiter of the one or more current limiters, such asdiscussed above in the context of at least FIGS. 1, 10-13, and 16-18.

In still even other embodiments, at least two battery cell segments ofthe plurality of battery cell segments are electrically connected usingone or more electrodes, such as discussed above in the context of atleast FIGS. 1, 10-13, and 16-18. In some of these embodiments, aparticular battery cell segment of the at least two battery cellsegments includes at least one of: an anode current collectorelectrically connected to the anode segment and to a negative electrodeof the one or more electrodes; and a cathode current collectorelectrically connected to the cathode segment and to a positiveelectrode of the one or more electrodes, such as discussed above in thecontext of at least FIGS. 1, 10-13, and 16-18. In other of theseembodiments, the anode current collector is electrically connected tothe negative electrode via an anode current limiter of the one or morecurrent limiters; and the cathode current collector is electricallyconnected to the positive electrode via a cathode current limiter of theone or more current limiters, such as discussed above in the context ofat least FIGS. 1, 10-13, and 16-18.

In yet even other of these embodiments, the anode segment is separatedfrom the cathode segment by a separator immersed in an electrolytefiller, where the one or more current limiters are connected to thecathode segment and/or the anode segment, and where the PTC layer ispositioned to separate a battery cell segment from other battery cellsegments of the plurality of battery cell segments, such as discussedabove in the context of at least FIGS. 16-18. For example, the separatorcan be made of one or more herein-described separator materials.

At block 2020, a particular battery cell segment can be conditionallyelectrically isolated based on an occurrence of a short circuit withinthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18. In some embodiments, conditionallyelectrically isolating the particular battery cell segment can includeconditionally electrically isolating the particular battery cell segmentusing a current limiter electrically connected to the anode segment ofthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18. In other embodiments, conditionallyelectrically isolating the particular battery cell segment can includeconditionally electrically isolating the particular battery cell segmentusing a current limiter electrically connected to the anode segment ofthe particular battery cell segment, such as discussed above in thecontext of at least FIG. 18.

In some embodiments, method 2000 can also include: electricallyisolating the particular battery cell segment from one or more otherbattery cell segments of the plurality of battery cell segments usingthe PTC material, such as discussed above in the context of at leastFIG. 18.

Disclosed embodiments are described above with reference to theaccompanying drawings, in which some, but not all of the disclosedembodiments may be shown. Indeed, several different embodiments may bedescribed and should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are described so that thisdisclosure are thorough and complete and convey the disclosure at leastto those skilled in the art.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent from the foregoing descriptions.Such modifications and variations are intended to fall within the scopeof the appended claims.

In addition, each block in the disclosed flowcharts may representcircuitry that is wired to perform the specific logical functions in theprocess. Alternative implementations are included within the scope ofthe example embodiments of the present disclosure in which functions maybe executed out of order from that shown or discussed, includingsubstantially concurrent or in reverse order, depending on thefunctionality involved, as would be understood by those reasonablyskilled in the art.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.

What is claimed is:
 1. A battery, comprising: one or more cells, eachcell comprising a plurality of battery cell segments electricallyconnected in parallel within the cell to electrodes, each battery cellsegment comprising: a positive temperature coefficient (PTC) materialwhose resistance increases with temperature, an anode segment, a cathodesegment, and one or more current limiters configured to conditionallyelectrically isolate the battery cell segment based on an occurrence ofa short circuit within the battery cell segment, wherein the anodesegment is separated from the cathode segment by a separator immersed inan electrolyte filler, wherein the one or more current limiters areconnected to the cathode segment and/or the anode segment, and whereinthe PTC material is positioned to separate a battery cell segment fromother battery cell segments of the plurality of battery cell segments.2. The battery of claim 1, wherein a current limiter of the one or morecurrent limiters comprises a fuse.
 3. The battery of claim 1, whereinthe PTC material is one or more of: thermoplastic polymer, bariumtitanate, barium carbonate, and titanium oxide.
 4. The battery of claim1, wherein the PTC material further includes an active material.
 5. Thebattery of claim 4, wherein the active material comprises a cathodeactive material associated with the cathode segment.
 6. The battery ofclaim 5, wherein the cathode active material comprises one or more of: amaterial including lithium cobalt oxide, a material including lithiumcobalt phosphate, a material including lithium iron oxide, a materialincluding lithium iron phosphate, a material including lithium ironsilicate, a material including lithium manganese dioxide, a materialincluding lithium manganese nickel oxide, and a material includinglithium manganese nickel oxide.
 7. The battery of claim 4, wherein theactive material comprises an anode active material associated with theanode segment.
 8. The battery of claim 7, wherein the anode activematerial comprises one or more of: a material including graphite and amaterial including lithium titanate.
 9. The battery of claim 1, whereineach battery cell segment further comprises one or more currentcollectors, and wherein the one or more current collectors comprise atleast one of: an anode current collector electrically connected to theanode segment; and a cathode current collector electrically connected tothe cathode segment.
 10. The battery of claim 9, wherein each batterycell segment further comprises: a current collector of the one or morecurrent collectors electrically connected to a current limiter of theone or more current limiters.
 11. The battery of claim 1, wherein aparticular battery cell segment of the at least two battery cellsegments comprises at least one of: an anode current collectorelectrically connected to the anode segment and to a negative electrodeof the one or more electrodes; and a cathode current collectorelectrically connected to the cathode segment and to a positiveelectrode of the one or more electrodes.
 12. The battery of claim 11,wherein the anode current collector is electrically connected to thenegative electrode via an anode current limiter of the one or morecurrent limiters; and wherein the cathode current collector iselectrically connected to the positive electrode via a cathode currentlimiter of the one or more current limiters.
 13. A battery, comprising:one or more cells, each cell comprising a plurality of battery cellsegments electrically connected in parallel within the cell toelectrodes, each battery cell segment comprising: a positive temperaturecoefficient (PTC) material whose resistance increases with temperature,an anode segment, a cathode segment, and one or more current limitersconfigured to conditionally electrically isolate the battery cellsegment based on an occurrence of a short circuit within the batterycell segment, wherein the PTC material is positioned to separate abattery cell segment from other battery cell segments of the pluralityof battery cell segments.
 14. The battery of claim 13, furthercomprising: multiple layers of PTC material positioned to separateneighboring battery cell segments.
 15. The battery of claim 13, furthercomprising: an insulator material positioned to separate a battery cellsegment from a neighboring battery cell segment in each cell.
 16. Thebattery of claim 13, wherein a current limiter of the one or morecurrent limiters comprises a fuse.
 17. The battery of claim 13, whereinthe PTC material is one or more of: thermoplastic polymer, bariumtitanate, barium carbonate, and titanium oxide.
 18. The battery of claim13, wherein the PTC material further includes an active material. 19.The battery of claim 18, wherein the active material comprises a cathodeactive material associated with the cathode segment.
 20. The battery ofclaim 18, wherein the active material comprises an anode active materialassociated with the anode segment.